Field of the Invention
The present invention relates to an image heating device to be preferably used as a fixing device provided in an image forming apparatus such as an electrophotographic copying machine and electrophotographic printer.
Description of the Related Art
In an image forming apparatus having an image heating device, when print processing is sequentially performed on a small-size recording material of a width narrower than a width of a recording material of a maximum width usable in the apparatuses, a phenomenon in which a temperature of the non-sheet passing part of a fixing unit rises (i.e., non-sheet-passing part temperature rise), occurs. In the technical field of film-heating fixing devices using a fixing film and a ceramic heater contacting the fixing film, as a method for reducing the non-sheet-passing part temperature rise, a method discussed in Japanese Patent Application Laid-Open No. 2003-317898 is proposed. In this method, a high thermal conductive member is held between a holding member for holding a heater and the heater to reduce unevenness in the temperature distribution of the heater.
Meanwhile, in assembling the apparatus, if a position of the high thermal conductive member is misaligned to the heater, temperatures at end portions in a longitudinal direction of the heater may decrease and this may deteriorate the fixation properties, and/or the effects of reducing the temperature rise in the non-sheet-passing part by the high thermal conductive member may decrease. Especially, when a thin sheet is used as the high thermal conductive member, the handling of the sheet is difficult, and consequently, at the time of assembly, it is difficult to determine the position of the sheet to the heater.